The present invention is directed to apparatus and methods for making reagent mixtures, and more particularly, to apparatus and methods for making a plurality of reagent mixtures and analyzing particle distributions of the reagent mixtures, such as for blood cell analysis.
Prior to the mid-1970s, red blood cell, platelet and white blood cell differential analyses were typically conducted by manual examination, with a technician viewing blood film slides with the aid of a microscope. Since that time, hematological analysis has been automated, making its use both widespread and commonplace.
While the methodologies for automated analysis vary, most often the enumeration and analysis involves subjecting a diluted sample of whole blood to a lysing reagent which stromatolyzes and eliminates the red blood cell population, and simultaneously modifies the cell membranes of the more prevalent white cell subpopulations. This causes differential shrinkage of the different cell types and enables discrimination and sorting thereof. The size and number of white blood cells in the sample are then detected with the aid of an automated analyzer, by pulling the sample fluid through a sensing zone, which is typically adapted to detect the size (volume) and/or opacity of the blood cells in the sample by electrical or optical differences. The blood cells are counted for a period of time sufficient to gather data for analysis, data points are stored in a memory device, and then analyzed in a processor. The data can then be displayed in the form of a two-dimensional or three-dimensional histogram.
There are various prior art devices for supplying sheath stream and sample fluids to the sensing aperture of a detector. U.S. Pat. No. 3,740,143 shows a system employing peristaltic pumping to supply a series of diluted blood samples to a flow cell for white blood cell differentiation and counting. Peristaltic pumping, which operates by the occlusion or squeezing of the pump tubes, does not provide a sufficiently steady-state flow, and can result in damage to the integrity of the cells, further degrading the accuracy of the device.
U.S. Pat. No. 4,695,431 also shows an apparatus for supplying fluids to a sheath stream flow cell, which employs a single piston pump to inject the sheath fluid into the flow cell with one side of the pump, and simultaneously aspirate the blood sample through the flow cell with the other side of the pump. The piston pump is driven by a drive cylinder operated by controlling the flow of pressurized fluid. By aspirating the blood sample through the flow cell, the suction forces can distort the cells, thus reducing the accuracy of the device. Also, because the single pump is driven by a pressurized cylinder, the fluid quantity cannot be controlled as accurately as may be desired.
For cell or particle analyses of this type, the present inventors have realized that it is advantageous to detect one cell at a time, and accumulate data on thousands of cells. Coincidence, or the simultaneous passage of multiple cells through the sensing zone, can create anomalies or aberrant information. Although this type of information can be partially corrected by using mathematical equations or pulse editing circuits when analyzing the data, important information about the cells may be rejected and thrown away with the sample. This may include information about abnormalities in the sample, since the abnormal cells may give rise to unusual pulses that are rejected in compensating for the passage of multiple cells through the sensing zone. The present inventors have realized that it would be desirable to provide a precisely controlled, steady-state flow of both blood sample and sheath fluids, wherein the sample cells are injected through the sensing zone in a substantially single-file relationship relative to each other in order to avoid coincidence and permit accurate detection of cell properties.
The present inventors have also realized that it would be desirable to provide an apparatus and method for hematology testing that may automatically adjust or create reagent mixtures corresponding to each of a plurality of different species.
The present invention is directed to an apparatus and method for making a plurality of reagent mixtures and analyzing particle distributions of the reagent mixtures, such as for blood cell analysis. The apparatus comprises at least one pump, such as a positive-displacement pump, a sensing unit defining a counting orifice for receiving a reagent mixture and analyzing a particle distribution of the reagent mixture, and a control unit, or like means, for adjusting the reagent mixture to correspond to each of a plurality of different operator inputs. The control unit controls one or more pumps to aspirate a predetermined quantity of each of a plurality of reagent-mixture components, wherein each predetermined quantity corresponds to the respective input, and further controls the pump or pumps to mix the aspirated components into the reagent mixture. The control unit then controls a pump to introduce the reagent mixture through the sensing unit for sensing a particle distribution of the reagent mixture, such as for blood cell analysis.
In one embodiment of the present invention, the plurality of inputs each correspond to a respective animal species, and for each input, the plurality of reagent-mixture components includes a first reagent-mixture component consisting essentially of a whole blood sample of the respective species, a second reagent-mixture component consisting essentially of diluent, and a third reagent-mixture component consisting essentially of a lysing agent for making a blood/diluent and/or a blood/diluent/lyse reagent mixture corresponding to the respective species. Also in an embodiment of the present invention, the control unit includes a database pertaining to predetermined quantities of lysing agents necessary for formulating blood/reagent mixtures for a plurality of species. The control unit is responsive to an input indicating a specific species to control one or more pumps to aspirate, predetermined quantities of the lysing agents from the first and second lysing containers corresponding to the respective species.
One advantage of the apparatus and method of the present invention is that the reagent mixture may be automatically adjusted to correspond to each of a plurality of different operator inputs, which may each correspond, for example, to a different animal species to automatically create the reagent mixture for each species.
Other advantages of the present invention will become apparent in view of the following detailed description and accompanying drawings.